This grant application requests funds for a five-year period for the coninued participation of Memorial Sloan-Kettering Cancer Center and its affiliate hospitals in Childrens Cancer Study Group. The overall objectives of this funded clinical research project are to improve the prognosis and survival of children with cancer through multidisciplinary collaborative treatment protocols. Secondary objectives include the study of the natural history and biology of pediatric malignancies, the clinical testing of Phase II agents after conventional therapy has failed, the long-term evaluation of late effects of cancer treatment, and the determination of the role of bone marrow transplantation in acute leukemia. Treatment protocols for previously untreated patients will be designed and implemented to take advantage of clinical and biological prognostic factors and to assign and stratify patients according to risk or prognostic groups. Study questions will be aimed at reducing the intensity and duration of therapy in patients with favorable prognostic features and at intensifying therapy in patients with a poor prognosis. Reference laboratories at MSKCC will review leukemic cell morphology using the FAB classification and will perform immunologic phenotyping of leukemic cells using monoclonal antibodies. The special clinical facilities and large patient population will be used to develop advanced pilot protocols for eventual groupwide use and to serve as a referral center for bone marrow transplantation. The clinical personnel have had extensive and proven experience in the design and implementation of innovative multidisciplinary protocols and will continue to provide scientific leadership for the Group by participation in Strategy Groups, Standing Committees and Study Committees. The affiliate network will be expanded and further upgraded and will serve as a source for increased patient entries on Groupwide studies.